The United States in recent years has been abandoning its historical role as a leader in environmental regulation. At the same time, the European Union, spurred by political integration, has enacted many new environmental laws and assumed a leadership role in promoting global environmental sustainability. Green Giants?, one of the most detailed comparisons of the environmental policies of America and Europe yet undertaken, looks at current policy trends in the United States and the European Union-the two largest economic actors in the world-and the implications they have for future transatlantic and global cooperation. The contributors-leading European and American scholars and practitioners-examine similarities and differences in specific policy areas in order to assess whether United States and European Union policies are diverging, pursuing similar goals and methods, or undergoing a "hybridization" through joint learning and exchanges. They find that although European and American policies may parallel each other somewhat in domestic regulation, they are clearly diverging in the "third generation" of environmental concerns, which include such global problems as climate change, international trade, and sustainable development. In the final chapter the editors conclude that transatlantic dialogue and cooperation at the highest level are necessary if these two economic and political giants are to lead the international community toward a stable and secure ecological future.